Abstract:
In recent decades supplementation of animal feeds with exogenous fibrolytic enzymes
has substantially improved digestibility and animal performance. However, information
related to associated methane production is limited and inconsistent. This study evaluated the
effect of cellulase and xylanase enzymes on in vitro methane production of Eragrostis curvula
hay, maize (Zea mays) stover and a total mixed ration (TMR) at seven levels of the two enzymes.
Feed samples were incubated for 2, 12, 24 and 48 h in an in vitro batch culture with buffer and
rumen fluid, and fibrolytic enzymes. Gas production was measured using a pressure transducer
connected to a data tracker, while methane gas was analysed using a gas chromatograph which
was calibrated with standard CH4 and CO2. Increases in the level of enzyme application resulted
in increases in gas volume, total volatile fatty acid (VFA) production, dry matter (DM) disappearance
and associated increases in methane production. The linear increase in percentage and
volume of methane production in tandem with increases in level of enzyme application might
be due to increased fermentation, and organic matter degradability that resulted in a shift in
VFA production towards acetate. Considering the efficiency of DM and neutral detergent fiber
degradation and production of associated VFA with levels of enzymes, the use of 1 mg g−1 DM
of enzyme can be a good option for the feeds tested. However, they cannot decrease methane
production. It will be very important to consider other hydrogen sinks that can capture directly
extra H+ produced by the addition of enzyme so that their supplementation could be very efficient
and environmentally sound.
